There are times when a tactical victoty can be a strategic error.
The example which one strategist like to tell is in teal war, if you have two units on a front line and one is more organised and better prepared, the other is full o fresh recruits who don't know what they are doing and lacks confidence.
Then your line is attacked. The disorganised unit retreats, while the organised one holds their ground. However the enemy advances and surrounds the organised unit, cutting them off and capturing them. A small tactial victory on the part of the organised unit defending their position and pushing back an enemy advance can lead to a much worse strategic position.
There are similar things you can do in diplomacy, but the combat is very abstracted, making the tactics as simple as possible, while still being highly engaging on a 1v1 level.
So, i'm going to take the extreme position that i don't count, gunboat, 1v1, Chaos, or scoring variants as 'diplomacy' (you can obviously have diplomacy on different maps, but 'pure' loses all geographic nuance - for those who don't know pure, it is 7 player, on 7 SC all connected to each other. No neutrals, no empty spaces, everyone can attack or support everyone else.)
That said, i think gunboat offers an excellent experience (though i don't think it is diplomacy, and i don't play gunboat myself) 1v1 games are great, i like them because they are fast and you get lots of fun out for the amount of time you put in. So my argument for what 'counts' isn't to say what we should allow on this site. Just to understand what different variants we should consider...
Are there any others type of variant, where you can take an aspect of diplomacy and reduce or enjance it to the extreme (map complexity reduce gives pure, i'm not sure about increasingly complex maps...)